If I am reading this right it looks like it does just hash some stuff and sends a hash. This one is not for anonymity as much as it is for securing the content between two users with the advanced DH ratchet and backward / forward / future secrecy. However even if the server were to log its basically 2 hashes talking to each other, still pretty difficult to tell what is what.

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@interface Contact : NSObject
@property (readonly,nonatomic) NSString *firstName;
@property (readonly,nonatomic) NSString *lastName;
@property (readonly,nonatomic) NSArray
*parsedPhoneNumbers;
@property (readonly,nonatomic) NSArray      *userTextPhoneNumbers;
@property (readonly,nonatomic) NSArray *emails;
@property (readonly,nonatomic) UIImage *image;
@property (readonly,nonatomic) NSString *notes;
@property (readonly,nonatomic) ABRecordID recordID;
+ (Contact*)contactWithFirstName:(NSString*)firstName
andLastName:(NSString *)lastName
andUserTextPhoneNumbers:(NSArray*)phoneNumbers
andEmails:(NSArray*)emails
andContactID:(ABRecordID)record;
+ (Contact*)contactWithFirstName:(NSString*)firstName
andLastName:(NSString *)lastName
andUserTextPhoneNumbers:(NSArray*)numbers
andEmails:(NSArray*)emails
andImage:(UIImage *)image
andContactID:(ABRecordID)record
andNotes:(NSString *)notes;
- (NSString*)fullName;
- (NSString *)allPhoneNumbers;
- (BOOL)isTextSecureContact;
- (BOOL)isRedPhoneContact;
- (NSArray*)textSecureIdentifiers;
- (NSArray*)redPhoneIdentifiers;
@end
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Fed to SHA1

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#pragma mark SHA1
+(NSString*)truncatedSHA1Base64EncodedWithoutPadding:(NSString*)string{
/* used by TSContactManager to send hashed/truncated contact list to server */
NSMutableData *hashData = [NSMutableData dataWithLength:20];
CC_SHA1([string dataUsingEncoding:NSUTF8StringEncoding].bytes,
(unsigned int)[string dataUsingEncoding:NSUTF8StringEncoding].length,
hashData.mutableBytes);
NSData *truncatedData = [hashData subdataWithRange:NSMakeRange(0, 10)];
return [[truncatedData base64EncodedString] stringByReplacingOccurrencesOfString:@"=" withString:@""];
}
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